3116X issues - Printable Version

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+--- Thread: 3116X issues (/showthread.php?tid=22354)

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3116X issues - Brad Winder - 04-01-2021

I am having an issue with the 3116 (116) I recently restored. It has been fully recapped, including all paper and electrolytic, plus three micas. All out-of-tolerance resistors changed, along with the Candohm. It plays beautifully, very good sound, selectivity great, nice tone. But...at low volume levels, there is a "clicking" noise. And, I have 64 volt AC on the chassis, measured to ground. I found this problem, after getting a small shock. And to top it off, if I connect a ground lead to the chassis, the audio develops a hiss and distortion, which stays even after I disconnect the ground. I need to shut off the set, and let it cool down, to get the audio back to normal. 

-I have eliminated the tubes as the issue; swapped all, one at a time, for known good ones. 

-Performed a dim-bulb test on the power transformer. All tubes/dial lamps removed. No glow with no load. And the voltage on the chassis is gone as well.

-"click" noise present with RF/IF sections disconnected. So, assuming it might be the audio output transformer, I checked it...no shorts detected. Even swapped an identical speaker assembly...same issues.

So...before I go and start ripping the chassis apart, or ripping out my hair, has anyone run into an issue like this? Steer me in the right direction?

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RE: 3116X issues - morzh - 04-01-2021

if you have 64VAC on the chassis (I take it you mean the Earth GND that you measured it in reference to) this could mean:

1. Capacitive divider 131 from L and N to chassis. This is normal. If you connect a say 10K resistor from it to GND it should go to zero.
2. Check your caps there for the value. 0.015uF is plenty. If you put some larger value - replace.
3. Simply ohm out the input plug to chassis, see if there is some finite resistance there.
4. A capacitive coupling to the chassis via transformer also could make 6oV but it should be extremely weak and not cause any feelings when touched.
5. Check the transformer for leakaga. (same as in bullet 3)

As for the clicking noise....short of pulling the output tubes, see what tube pulling stops it. if does not, pull the output tubes, one by one. Always leave one tube in.

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RE: 3116X issues - Brad Winder - 04-07-2021

Thanks for the help, morzh! I forgot to mention that I did pull the tubes, and the "clicking" is still present, unless I pull out the 42 .

But I got the probe I was building for my Eico signal tracer finished, and low and behold...the clicking noise comes through on the tracer, without the radio plugged in. So, I did some checking, and the noise is on the power line to my basement shop! But not present anywhere else in the house. My shop is on a sub panel, so that may be a cause. I have a my personal Sparky on the case. He thinks it may be an induced noise, from another line that crosses the supply to my panel. We'll see...

I may have isolated the voltage issue, however, after I followed your advice. I believe I may have a leaking mica cap, off the grid of the 77 tube.

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